The present invention relates to arthodesis for stabilizing the spine. More specifically, the present invention is directed to an intervertebral spacer formed of a bone material and to methods of treating patients having spinal deformities.
Removal of damaged or diseased discs and restoration of disc space height to treat chronic back pain and other ailments are known medical techniques. Implants such as intervertebral spacers are often implanted in the disc space to maintain or reestablish disc space height after removal of all or a portion of the disc. The spacers can be formed of a variety of both resorbable and non-resorbable materials, including, for example, titanium, surgical steel, polymers, composites, and bone. It is also often desirable to promote fusion between the vertebral bodies that are adjacent to the damaged or diseased discs. Typically an osteogenic material is combined with a spacer and inserted in the disc space to facilitate and promote bone growth. While the selection of the implant configuration and composition can depend upon a variety of considerations, for arthodesis it is often desirable to select a resorbable material than does not stress shield the bone ingrowth. Bone and bone-derived components can provide suitable material to prepare the implants. However, bone material acceptable for use in implants is a scarce resource, being derived from limited human tissue donor resources.
Suitable bone or bone-derived material for use in implants, in general, is almost exclusively obtained from allograft and xenograft sources, both which are precious resources. Since intervertebral spacers must withstand the compressive loads exerted by the spine, these implants are often formed from cortical long bones, which are primarily found in the lower limbs and include, for example, femur, fibula, and the tibia bones. The long bones make up only a fraction of the available bone source. Thus, sources of bone suitable for structural intervertebral spacers are extremely limited. The scarcity of desired donor bone makes it difficult to provide implants having the desired size and configuration for implantation between adjacent lumbar vertebrae, which can require relatively large implants. It is further anticipated that as the population ages there will be an increased need for correction for spinal deformities and a concomitant increase in the demand for bone-derived components. Therefore, these structural bone portions must be conserved and used efficiently to provide implants. The scarcity of suitable bone material has also hindered efforts to design and manufacture varying configurations of suitable implants for arthodesis of the spine. Further, various implant configurations have not been physiologically possible to obtain given the structural and geometrical constraints of available donor bone.
In light of the above-described problems, there continues to be a need to provide suitable implants to facilitate patient treatment. The present invention addresses this need and provides a variety of other benefits and advantages.